Determining an angle between a tow vehicle and a trailer

ABSTRACT

The angle of a trailer with respect to a tow vehicle is an important parameter to the stability of the vehicle and trailer. A tow vehicle pulling a trailer in a straight line is generally more stable than when the vehicle is turning. While turning, the angle between the tow vehicle and the trailer is not a straight line but is another angle depending on how sharply the tow vehicle is turning. To safely operate a vehicle towing a trailer, for a given steering input and speed, there is a maximum angle between the tow vehicle and trailer whereby exceeding the angle causes instability and may cause the trailer or tow vehicle to roll over or jackknife. Accordingly, the angle between the trailer and tow vehicle must be determined to ensure the vehicle and trailer will continue to be in control.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/174,980, titled “DETERMINING AN ANGLE BETWEEN A TOW VEHICLE AND ATRAILER,” filed on Oct. 30, 2018, published as U.S. Pre-GrantPublication 2020-0132835 on Apr. 30, 2020, the disclosure of which ishereby incorporated by reference in its entirety herein.

TECHNICAL FIELD

This document relates to determining the angle between a tow vehicle anda trailer being towed.

BACKGROUND

Many different types of vehicles are used to tow a variety of differenttypes of trailers. For example, commercial semi-trailer trucks, alsoknown as semis, tractor-trailers, big rigs, eighteen-wheelers, ortransports include a tractor towing one or more trailers. Othernon-commercial vehicles such as pick-up trucks, motorhomes, recreationalvehicles, and sport-utility vehicles also tow trailers, boats, campers,and other types of trailers. In each of the above examples, thestability of the trailer and tow vehicle depends on multiple factorssuch as the speed of the trailer and tow vehicle, the weather conditionssuch as wind and rain, the length of trailer, the number of axles, theangle between tow vehicle and the trailer, and others. New techniquesare needed to measure the angle between the trailer and tow vehicle thatare reliable, accurate, have a long service life, and are inexpensive.

SUMMARY

Disclosed are devices, systems and methods for determining an angle suchas the angle that a trailer is towed behind a vehicle. In one aspect, asystem for determining a trailer angle between a trailer and a vehicleis disclosed. The system includes one or more ultrasonic sensors,wherein each ultrasonic sensor is mountable to the vehicle to determinea distance from the ultrasonic sensor to a front-end of a trailerattached to the vehicle. The system further includes an ultrasoniccontrol unit configured to receive the distance from each of the one ormore ultrasonic sensors via a communications interface, wherein theultrasonic control unit determines one or more angles, each anglecorresponding to a distance received from the one or more ultrasonicsensors, wherein each angle is between the vehicle and the trailer, andwherein the ultrasonic control unit determines the trailer angle fromthe one or more angles.

In another aspect, a method for determining a trailer angle between atrailer and a vehicle is disclosed. The method includes receiving, fromeach of one or more ultrasonic sensors attached to the vehicle,information about a distance between each ultrasonic sensor and afront-end of the trailer attached to the vehicle, and determining one ormore angles, each angle corresponding to the information about thedistance received from the one or more ultrasonic sensors, wherein eachangle is an estimate of alignment between the vehicle and the trailer,and wherein a trailer angle is determined from the one or more angles.

In another aspect, a non-transitory computer readable medium isdisclosed. The non-transitory computer readable medium stores executableinstructions for determining a trailer angle between a trailer and avehicle that when executed by at least one processor perform at leastthe following: receiving, from each of one or more ultrasonic sensors, adistance between each ultrasonic sensor and a front-end of the trailerattached to the vehicle, and determining one or more angles, each anglecorresponding to a distance received from the one or more ultrasonicsensors, wherein each angle is between the vehicle and the trailer, andwherein a trailer angle is determined from the one or more angles.

The following features can be included in various combinations. A firstangle corresponding to a first ultrasonic sensor can be determined basedon one or more geometrical relationships between a position of the firstultrasonic sensor and the front-end of the trailer. The trailer anglecan be determined as an average angle of the one or more angles. Theaverage angle can be weighted based on a standard deviation for distancevalues received at the ultrasonic control unit from each of the one ormore ultrasonic sensors. The ultrasonic control unit can determine anerror interval and a confidence level based on the standard deviationfor distance values received at the ultrasonic control unit from each ofthe one or more ultrasonic sensors. The first angle can be determinedfrom: a first neutral distance between the first ultrasonic sensor andthe front-end of the trailer when the trailer is in line with thevehicle, a first angled distance when the trailer is angled with respectto the vehicle, and/or a first offset distance between the center of thefirst ultrasonic sensor and the center of the tractor. The first neutraldistance can be determined when a steering angle of the vehicle is aboutzero degrees and the vehicle is travelling at about 10 kilometers perhour or more. The ultrasonic control unit can include at least oneprocessor, at least one memory storing executable instructions that whenexecuted by the at least one processor perform at least the followingdetermining the first angle corresponding to a first ultrasonic sensoras: A₁=arctangent ((D₁₋₁−D₁₋₂)/Dis1), wherein A₁ is the first anglebetween the vehicle and the trailer, wherein D₁₋₁ is a first neutraldistance between the first ultrasonic sensor and the front-end of thetrailer, wherein the first neutral distance is determined when thetrailer is in line with the vehicle, wherein D₁₋₂ is a first angleddistance between the first ultrasonic sensor and the front-end of thetrailer, wherein the first angled distance is determined when thetrailer is angled with respect to the vehicle, and wherein Dis1 is afirst offset distance, wherein the first offset distance is between thecenter of the first ultrasonic sensor and the center of the vehicle.

The above and other aspects and features of the disclosed technology aredescribed in greater detail in the drawings, the description and theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example of an angle measurement system installed on atractor, in accordance with some example embodiments;

FIG. 2 depicts an example of an arrangement of ultrasonic sensors formeasuring an angle between a tow vehicle and a trailer, in accordancewith some example embodiments;

FIG. 3A depicts an illustration showing a trailer at an angle to a towvehicle that is not a straight line, and various distances, inaccordance with some example embodiments;

FIG. 3B depicts another illustration showing a trailer at an angle to atow vehicle, in accordance with some example embodiments;

FIG. 4 depicts an example of an apparatus, in accordance with someexample embodiments;

FIG. 5 depicts an example of an apparatus where two sensors are notoperational, in accordance with some example embodiments;

FIG. 6 depicts an example of an apparatus where four sensors are notoperational, in accordance with some example embodiments;

FIG. 7 depicts an example of a process, in accordance with some exampleembodiments; and

FIG. 8 depicts an example of an apparatus, in accordance with someexample embodiments.

DETAILED DESCRIPTION

The angle of a trailer with respect to a tow vehicle is an importantparameter to the stability of the vehicle and trailer. A tow vehiclepulling a trailer in a straight line is generally more stable than whenthe vehicle is turning. While turning, the angle between the tow vehicleand the trailer is not a straight line but is another angle depending onhow sharply the tow vehicle is turning. To safely operate a vehicletowing a trailer, for a given steering input and speed, there is amaximum angle between the tow vehicle and trailer whereby exceeding theangle causes instability and may cause the trailer or tow vehicle toroll over or jackknife. Accordingly, the angle between the trailer andtow vehicle may be determined to ensure the vehicle and trailer willcontinue to be in control. A trailer angle sensor system should providehigh accuracy and redundancy to ensure the system is always operableeven when one or more sensors are inoperable. This calculation becomesimportant when the vehicle is an autonomous vehicle and therefore lacksthe benefit of judgment of a human driver regarding stability of thecombination of the vehicle and the trailer when driving around curves.

Current trailer angle sensors have several limitations including: 1)Current trailer angle sensors need to be installed in trailers or atleast have to be fixed to the trailer in order to determine the relativemotion between trailer and tractor. This means the sensor needs to bereinstalled or recalibrated each time after changing the trailer; 2)Current techniques offer no redundancy since they use Hall effectdevices or resistive position sensors; 3) The lifecycle of currenttrailer angle sensors is limited because they are typically mounted nearthe 5^(th) wheel which is often a harsh environment due to vibration,exposure to the elements, and chemicals such as lubricating grease.

FIG. 1 depicts an example of an angle measurement system installed on atow vehicle (also referred to herein as a “tractor”), in accordance withsome example embodiments. Tractor 110 is physically coupled to trailer120. A side-view is shown at 100A, a top-view at 100B, a front-view at100C, and a back-view at 100D. The tractor 110 includes a plurality ofultrasonic sensors 130 mounted to the back of the tractor with theultrasonic beams directed to the front surface of the trailer. Each ofthe ultrasonic sensors determines or helps to determine the distancefrom the ultrasonic sensor to the front of the trailer 120. Using thedistances, ultrasonic control unit 125 determines the angle between thetractor and the trailer. In FIG. 1 , the tractor and trailer lie in astraight line. When the tractor trailer is turning, the tractor andtrailer may no longer be in line and there would be an angle between thetractor and trailer (also referred to as the “trailer angle”). UCU 125may include a processor and memory, and various interfaces such as oneor more communications interfaces.

FIG. 2 depicts an example of an arrangement of ultrasonic sensors formeasuring an angle between a tow vehicle and a trailer. In some exampleembodiments, the ultrasonic sensors 130 may be arranged as shown at 200.The sensor arrangement shown is an “inverted V” arrangement. Forexample, on the back of tractor 110 in FIG. 1 , the five ultrasonicsensors 131-135 may be mounted in the “inverted V” configuration withultrasonic sensor 133 highest above the roadway in the center(left-to-right) of the tractor, and ultrasonic sensors 131 and 135mounted on the back of the tractor closest to the roadway compared toultrasonic sensors 132-134. Although five sensors are shown at 200, agreater or smaller number of sensors may be used. Although theultrasonic sensors 131-135 are shown in an “inverted V” configuration,the sensors may be attached in a different configuration, such as astraight line (flat or tilted), a “W” or “inverted W” configuration orin another pattern. Organizing ultrasonic sensors in a two-dimensionalpattern in a plane that is perpendicular to the axis between the tractorand the trailer may lead to a more robust determination of the trailerangle. For example, placing the ultrasonic sensors in a pattern canavoid objects between the tow vehicle and trailer and can avoid surfacesthat are not normal to the ultrasonic sensor ultrasound when the traileris pulled in a straight line. These non-perpendicular surfaces may notbe suitable for ultrasonic distance determination. For example, anobject with an angled surface (non-perpendicular to illuminatingultrasound) attached to the trailer may be at an obtuse angle to anultrasonic sensor at a range of trailer angles causing the distancedetermined by the ultrasonic sensor to be inaccurate or preventing adistance from being determined due to little or no reflected ultrasonicsignal from the angled object. In some example embodiments, ultrasonicsensor may be oriented to illuminate the trailer with ultrasound at aperpendicular angle when the trailer angle is not zero degrees. By doingso, some ultrasonic sensors may provide better distance determinationsat different trailer angles. In some example embodiments, the ultrasonicsensors may provide timing information such as a transmit time and areception time from which a transit time to from the sensor to thetrailer can be determined, or some ultrasonic sensors may determine thetransit time. Form the transit time, the distance can be determinedbased on the speed of the ultrasound.

At 210 is an example illustration of a top-view of a tractor trailershowing ultrasonic sensors 131-135. Also shown are distances 201-205from each ultrasonic sensor to the front of the trailer 120. Distances201-205 may be referred to “neutral distances” because the trailer is ina straight line with the tow vehicle. Each ultrasonic sensor determinesinformation indicative of the distance, or the distance between thesensor to the front of the trailer. As noted above, informationindicative of the distance includes a transit time for the ultrasound topropagate to the trailer (one way or round trip) or timing informationsuch as time stamps from which the transit time can be determined. Inthe following, “distance” is used, but as noted above time informationcan be provided by the sensor instead of distance. For example,ultrasonic sensor 131 determines that the trailer is distance 201 fromultrasonic sensor 131. Ultrasonic sensor 132 determines that the traileris distance 202 from ultrasonic sensor 132. Ultrasonic sensor 133determines that the trailer is distance 203 from ultrasonic sensor 133.Ultrasonic sensor 134 determines that the trailer is distance 204 fromultrasonic sensor 134, and ultrasonic sensor 135 determines that thetrailer is distance 205 from ultrasonic sensor 135. With the tractor 110and trailer 120 in a straight line as shown at 210, the distances201-205 are approximately equal. In some embodiments, a fairing, winddeflector, or equipment such as cooling equipment for the trailer 120may cause the distances 201-205 to not be equal when the trailer andtractor lie in a straight line. The non-equal distances can be correctedin the UCU. The distances are provided to the UCU. The UCU may controlthe ultrasonic sensors and may receive health and status informationfrom the ultrasonic sensors.

FIG. 3A depicts an example illustration showing an example of a trailerat an angle to a tow vehicle that is not a straight line, and variousdistances. At 310 is an illustration of a tractor 110 with a trailer 120at an angle, trailer angle 350, to the trailer with ultrasonic sensors131-135 attached to tractor 110. Each ultrasonic sensor determines thedistance between the sensor to the front of the trailer as describedabove. In the example of FIG. 3A at 310, distance 301 is greater thatdistance 302, distance 302 is greater than distance 303, distance 303 isgreater than distance 304, distance 304 is greater than distance 305.Distances 201-205 may be referred to “angled distances” because thetrailer is not in a straight line with the tow vehicle. The distancesare provided by ultrasonic sensors 131-135 to the UCU 125 and are usedto determine the angle between the tractor 110 and trailer 120.

Shown at 320 is an illustration depicting distances 311-314 between thecenter of the center ultrasonic sensor 133 and the other ultrasonicsensors 131, 132, 134, and 135. Distances 311-314 are used indetermining the angle between tractor 110 and trailer 120. Althoughdistances 311-314 are shown from the center of one sensor to the centerof another, other distances related to the spacing of the ultrasonicsensors may be used instead.

The UCU coordinates distance measuring by the sensors and determines thetrailer angle based on the distances from the sensors. Coordination mayinclude turning-on the sensors 131-135 individually at different timesto prevent interference that could occur if multiple sensors wereoperating at the same time. In some example embodiments, the ultrasonicsensors may include a signature such as a pseudo-random noise (PN) codeor other code, or the different sensors may modulate the emittedultrasound to be orthogonal to other sensors. The UCU may also receiveinformation including vehicle speed information, steering angleinformation, and the UCU may make zero clearing based on adapted controlalgorithm. The trailer angle may be sent to a vehicle dynamicscontroller, electronic stability controller (ESC), or vehicle stabilitycontroller (VSC) of the tow vehicle.

FIG. 3B depicts another illustration showing a trailer at an angle to atow vehicle, in accordance with some example embodiments. FIG. 3B showsdistances and angles related to determining the trailer angle and isfurther described below with respect to Equation 1.

FIG. 4 at 400 depicts an apparatus, in accordance with some exampleembodiments. FIG. 4 includes ultrasonic sensors 131-135, ultrasoniccontrol unit (UCU) 125, vehicle speed sensor 410, steering angle sensor420, and vehicle dynamics controller 430.

Ultrasonic sensors 131-135 include a communications interface tocommunicate with UCU 125. For example, commands such as powering-up ordown each ultrasonic sensor, commanding each sensor to take a distancemeasurement, commands related to averaging distance values at eachsensor, and others may be sent from UCU 125 to the ultrasonic sensors131-135 individually or together. Data may be sent from each ultrasonicsensor to the UCU such as distance data, and sensor status and healthinformation. UCU 125 may perform a process to determine the trailerangle. The UCU may receive vehicle speed information from the vehiclespeed sensor 410 and/or steering angle information from steering anglesensor 420 via a dedicated or standard interface such as an on-boarddiagnostics (OBD) or another interface. The UCU may interface to avehicle dynamics controller such as ESC or VSC or other stabilitymanagement device in the vehicle.

FIG. 5 depicts an example of an apparatus where two sensors are notoperational, in accordance with some example embodiments. In the exampleof FIG. 5 , ultrasonic sensors 132A and 134A are not operational due toone or more types of failures. The UCU may use data from the remainingsensors 131, 133, and 135 to determine the trailer angle. Use of fewerultrasonic sensors (3 instead of 5) may cause a reduction in theaccuracy or resolution of the trailer angle, but may be sufficient tooperate the tractor trailer safely. FIG. 5 is an illustrative examplewhere two ultrasonic sensors are inoperable. Other combinations ofsensors may fail resulting in similar reduced performance as well.

FIG. 6 depicts an example of an apparatus where four sensors are notoperational, in accordance with some example embodiments. In the exampleof FIG. 6 , ultrasonic sensors 132A. 133A, 134A, and 135A are notoperational due to a one or more types of failures. The UCU may use datafrom the remaining sensor 131 to determine the trailer angle. Use offewer ultrasonic sensors (1 instead of 5) may cause a reduction in theaccuracy or resolution of the trailer angle, but may be sufficient tooperate the tractor trailer safely. FIG. 6 is an illustrative examplewhere four ultrasonic sensors are inoperable. Other combinations ofsensors may fail resulting in reduced performance as well.

FIG. 7 depicts a process 700, in accordance with some exampleembodiments. The trailer angle may be determined using the process 700.

At 710, the process includes determining, by the ultrasonic sensors131-135, the distances 201-205 to the trailer when trailer is in aneutral position (the trailer is in line with tractor). These values maybe sent to the UCU and stored in memory such as a nonvolatile memory inthe UCU. The neutral position may be determined when the steering angleis near zero and the tractor trailer velocity is greater than about 10km/h. The distance values may be averaged or filtered over a period oftime such as 1-5 seconds (or another time period). These stored valuesmay be used as long as the tractor is attached to the same trailer. If anew trailer is attached to the tractor or the trailer is removed andthen re-attached, the neutral distances may be determined again.

At 720, the trailer angle may be determined based the current distances301-305, the geometrical relationships between the sensors and thetractor and trailer, and the distances determined at 710. As the tractortrailer travels, the ultrasonic sensors 131-135 periodically,intermittently, or continuously determine the distances between thetractor and trailer. When the tractor turns, the determined distanceschange. For example, when the FIG. 3A tractor 110 and trailer 120 turnleft (as viewed from the top), distance 301 is greatest, followed by302, 303, 304, and 305 which is the smallest distance. If the tractorwere turning right, distance 305 would be greatest, 301 the smallest,and so on. In some example embodiments, angles may be determined forultrasonic sensors 131, 132, 134, and 135 but not sensor 133 which maybe used for initial angle determination.

Referring to FIGS. 3A and 3B, the following equation may be used todetermine the trailer angle at a first ultrasonic sensor:A ₁=arctan((D ₁₋₁ −D ₁₋₂)/Dis1)  Equation 1where A₁ refers to the trailer angle 350B in FIG. 3B at ultrasonicsensor 131, distance D₁₋₁ is distance 301, distance D₁₋₂ is distance302, distance D₁₋₁−D₁₋₂ is distance 330, and distance Dis1 is distance311. By symmetry angles 350A and 350B have the same value which is equalto the trailer angle. A similar equation may be expressed for angles atadditional ultrasonic sensors as A₂, A₃, and so on where A₂ refers tothe trailer angle at ultrasonic sensor 132, and so on, D₂₋₁ is distance202, and so on, D₂₋₂ is distance 302, and so on, and Dis2 is distance312, Dis4 is distance 313, and Dis5 is distance 314, and so on.

At 730, for each angle value (A₁, A₂, A₄, and A₅) a standard deviationSD₁, SD₂, SD₄, SD₅, may be determined. The noise from each ultrasonicsensor may be used to determine the standard deviation.

An average value may be determined for 100 angle determinations of A₁from:

$\begin{matrix}{\underset{\_}{A_{1}} = \frac{{A1_{1}} + {A1_{2}} + \ldots + {A\; 1_{100}}}{100}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

The standard deviation may then be expressed as:

$\begin{matrix}{{SD_{1}} = \sqrt{\frac{\left( {{A\; 1_{1}} - \underset{\_}{A\; 1}} \right)^{2} + \ldots + \left( {{A\; 1_{100}} - \underset{\_}{A\; 1}} \right)^{2}}{100}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

At 740, a weighting of the determined angle values from the differentultrasonic sensors based on their standard deviations may be expressedas:W ₁=1−SD ₁/(SD ₁ +SD ₂ +SD ₄ +SD ₅)W ₂=1−W ₁ −SD ₂/(SD ₂ +SD ₄ +SD ₅)W ₄=1−W ₁ −W ₂ −SD ₄/(SD ₄ +SD ₅)W ₅=1−W ₁ −W ₂ −W ₄  Equations 4

Because the back of the tractor and the front of the trailer arestructural and essentially rigid, in a perfect world without noise andimperfections, angles A₁, A₂, A₄, and A₅ would have the same value, butbecause of noise and imperfections they may differ in average and thestandard deviation of each is a measure of the “noisiness” of each.

At 760, a weighted trailer angle may be expressed as:A _(O) =W ₁ *A ₁ +W ₂ *A ₂ +W ₄ *A ₄ +*A ₅  Equation 5

At 770, an error and confidence level of the weighted trailer angle maybe expressed as:A _(Error) =W ₁ *SD ₁ +W ₂ *SD ₂ +W ₄ *SD ₄ +W ₅ *SD ₅  Equation 6A _(CL)=[A _(O) −A _(Error) ,A _(O) +A _(Error)]  Equation 7

In some example embodiments, zero detection of the trailer angle may beperformed. To begin zero detection, an error between the last angleoutput and current angle value may be 5 degrees or larger (or anothervalue such as 4 degrees). Ultrasonic sensor 133 may be used as aninitial reference of a zero angle for the other ultrasonic sensors.During the zero detection, each angle may be calculated using thefollowing formulas:A ₁=arctan((D ₁₋₂ −D ₃₋₁)/Dis1)A ₂=arctan((D ₂₋₂ −D ₃₋₁)/Dis2)A ₄=arctan((D ₄₋₂ −D ₃₋₁)/Dis4)A ₅=arctan((D ₅₋₂ −D ₃₋₁)/Dis5),  Equations 8where D₁₋₂, D₂₋₂, D₄₋₂, D₅₋₂ are the current distance measurements ofsensors 131, 132, 134, and 135, respectively. Sensor 133 may be mountedin the middle of the tractor as shown in FIGS. 3A and 3B. The relativemovement of the trailer and/or trailer angle will not influence, or willnegligibly influence, the distance measured by sensor 133. Accordingly,sensor 133 may be used as a reference for the system and to compare tothe distances from sensors 131, 132, 134, and 135.

In some example embodiments, a process 700 may be performed to determinea trailer angle between a trailer and a vehicle. At 720, the processincludes receiving, from each of one or more ultrasonic sensors, adistance between each ultrasonic sensor and a front-end of the trailerattached to the vehicle. At 720, the process includes determining one ormore angles, each angle corresponding to a distance received from theone or more ultrasonic sensors, wherein each angle is between thevehicle and the trailer, and wherein a trailer angle is determined fromthe one or more angles. The process may further include featuresdescribed above in various combinations.

FIG. 8 depicts an example of an apparatus 800 that can be used toimplement some of the techniques described in the present document. Forexample, the hardware platform 800 may implement the process 700, orother processes described above, and/or may implement the variousmodules described herein. The hardware platform 800 may include aprocessor 802 that can execute code to implement a method. The hardwareplatform 800 may include a memory 804 that may be used to storeprocessor-executable code and/or store data. The hardware platform 800may further include a communication interface 806. For example, thecommunication interface 806 may implement one or more wired or wirelesscommunication protocols (Ethernet, LTE, Wi-Fi, Bluetooth, and so on).

Implementations of the subject matter and the functional operationsdescribed in this patent document can be implemented in various systems,semiconductor devices, ultrasonic devices, digital electronic circuitry,or in computer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. Implementations of aspects of thesubject matter described in this specification can be implemented as oneor more computer program products, e.g., one or more modules of computerprogram instructions encoded on a tangible and non-transitory computerreadable medium for execution by, or to control the operation of, dataprocessing apparatus. The computer readable medium can be amachine-readable storage device, a machine-readable storage substrate, amemory device, a composition of matter effecting a machine-readablepropagated signal, or a combination of one or more of them. The term“data processing unit” or “data processing apparatus” encompasses allapparatus, devices, and machines for processing data, including by wayof example a programmable processor, a computer, or multiple processorsor computers. The apparatus can include, in addition to hardware, codethat creates an execution environment for the computer program inquestion, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, or acombination of one or more of them.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of nonvolatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any invention or of what may beclaimed, but rather as descriptions of features that may be specific toparticular embodiments of particular inventions. Certain features thatare described in this patent document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described, and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A system for determining a trailer angle betweena trailer and a vehicle, comprising: one or more ultrasonic sensors,wherein each ultrasonic sensor is mountable to the vehicle to determinea distance from the ultrasonic sensor to a front-end surface of thetrailer attached to the vehicle, and wherein the distance is orientednormal to the vehicle; and an ultrasonic control unit configured toreceive the distance from each of the one or more ultrasonic sensors viaa communications interface, wherein the ultrasonic control unitdetermines one or more angles, each angle corresponding to a distancereceived from the one or more ultrasonic sensors, wherein each angle isbetween the vehicle and the trailer, and wherein the ultrasonic controlunit determines the trailer angle from the one or more angles, wherein afirst angle corresponding to a first ultrasonic sensor is determinedbased on one or more geometrical relationships between a position of thefirst ultrasonic sensor and the front-end surface of the trailer.
 2. Thesystem of claim 1, wherein the first angle is determined from: a firstneutral distance between the first ultrasonic sensor and the front-endsurface of the trailer when the trailer is in line with the vehicle, afirst angled distance when the trailer is angled with respect to thevehicle, and a first offset distance between a center of the firstultrasonic sensor and a center of the vehicle.
 3. The system of claim 2,wherein the first neutral distance is determined when a steering angleof the vehicle is about zero degrees and the first neutral distance isaveraged or filtered over a period of time.
 4. The system of claim 3,wherein the ultrasonic control unit comprises: at least one processor;and at least one memory storing executable instructions that whenexecuted by the at least one processor perform at least: determining thefirst angle corresponding to a first ultrasonic sensor as:A ₁=arctangent((D ₁₋₁ −D ₁₋₂)/Dis1), wherein A₁ is the first anglebetween the vehicle and the trailer, wherein D₁₋₁ is a first neutraldistance between the first ultrasonic sensor and the front-end surfaceof the trailer, wherein the first neutral distance is determined whenthe trailer is in line with the vehicle, wherein D₁₋₂ is a first angleddistance between the first ultrasonic sensor and the front-end surfaceof the trailer, wherein the first angled distance is determined when thetrailer is angled with respect to the vehicle, and wherein Dis1 is afirst offset distance, wherein the first offset distance is between thecenter of the first ultrasonic sensor and the center of the vehicle. 5.The system of claim 2, wherein the first neutral distance is determinedwhen: a steering angle of the vehicle is about zero degrees, and thevehicle is travelling about 10 kilometers per hour or more.
 6. Thesystem of claim 1, wherein the trailer angle is determined as an averageangle of the one or more angles.
 7. The system of claim 6, wherein theaverage angle is weighted based on a standard deviation for distancevalues received at the ultrasonic control unit from each of the one ormore ultrasonic sensors.
 8. The system of claim 7, wherein theultrasonic control unit determines an error interval and a confidencelevel based on the standard deviation for distance values received atthe ultrasonic control unit from each of the one or more ultrasonicsensors.
 9. The system of claim 1, wherein the one or more ultrasonicsensors comprise a plurality of ultrasonic transducers mounted to thevehicle in an inverted “V” pattern, a “W” pattern, or an inverted “W”pattern.
 10. A method for determining a trailer angle between a trailerand a vehicle, comprising: receiving, from each of one or moreultrasonic sensors attached to the vehicle, information about a distancebetween each ultrasonic sensor and a front-end surface of the trailerattached to the vehicle, and wherein the distance is oriented normal tothe vehicle; and determining one or more angles, each anglecorresponding to the information about the distance received from theone or more ultrasonic sensors, wherein each angle is an estimate ofalignment between the vehicle and the trailer, and wherein a trailerangle is determined from the one or more angles.
 11. The method of claim10, wherein a first angle corresponding to a first ultrasonic sensor isdetermined based on one or more geometrical relationships between aposition of the first ultrasonic sensor and the front-end surface of thetrailer.
 12. The method of claim 11, wherein the first angle isdetermined from: a first neutral distance between the first ultrasonicsensor and the front-end surface of the trailer when the trailer is inline with the vehicle; a first angled distance when the trailer isangled with respect to the vehicle; and a first offset distance betweena center of the first ultrasonic sensor and a center of the vehicle. 13.The method of claim 12, wherein the first neutral distance is determinedwhen a steering angle of the vehicle is about zero degrees and thevehicle is travelling at about 10 kilometers per hour or more.
 14. Themethod of claim 11, further comprising: determining the first anglecorresponding to a first ultrasonic sensor as:A ₁=arctangent((D ₁₋₁ −D ₁₋₂)/Dis1), wherein A₁ is the first anglebetween the vehicle and the trailer, wherein D₁₋₁ is a first neutraldistance between the first ultrasonic sensor and the front-end surfaceof the trailer, wherein the first neutral distance is determined whenthe trailer is in line with the vehicle, wherein D₁₋₂ is a first angleddistance between the first ultrasonic sensor and the front-end surfaceof the trailer, wherein the first angled distance is determined when thetrailer is angled with respect to the vehicle, and wherein Dis1 is afirst offset distance, and wherein the first offset distance is betweena center of the first ultrasonic sensor and a center of the vehicle. 15.The method of claim 11, wherein the one or more ultrasonic sensors arein a two-dimensional pattern in a plane that is perpendicular to an axisbetween the vehicle and the trailer.
 16. The method of claim 10, whereinthe trailer angle is determined as an average angle of the one or moreangles.
 17. The method of claim 16, wherein the average angle isweighted based on a standard deviation for distance values received fromeach of the one or more ultrasonic sensors.
 18. The method of claim 17,wherein an error interval and a confidence level is determined based onthe standard deviation for the distance values received from each of theone or more ultrasonic sensors.
 19. A non-transitory computer readablemedium storing executable instructions for determining a trailer anglebetween a trailer and a vehicle that when executed by at least oneprocessor perform at least: receiving, from each of one or moreultrasonic sensors, a distance between each ultrasonic sensor and afront-end surface of the trailer attached to the vehicle, and whereinthe distance is oriented normal to the vehicle; determining one or moreangles, each angle corresponding to a distance received from the one ormore ultrasonic sensors, wherein each angle is between the vehicle andthe trailer, and determining a first angle corresponding to a firstultrasonic sensor based on one or more geometrical relationships betweena position of the first ultrasonic sensor and the front-end surface ofthe trailer.
 20. The non-transitory computer readable medium of claim18, wherein the first angle is determined from: a first neutral distancebetween the first ultrasonic sensor and the front-end surface of thetrailer when the trailer is in line with the vehicle, a first angleddistance when the trailer is angled with respect to the vehicle, and afirst offset distance between a center of the first ultrasonic sensorand a center of the vehicle, wherein a trailer angle is determined fromthe one or more angles.